The present invention relates to a rear sub frame of an automotive vehicle, and in particular relates to the rear sub frame of the automotive vehicle, which is attached to a kick-up portion and rear frames of a vehicle body at a rear portion of the vehicle body where a rear differential is provided.
An assembly of an automotive vehicle, in which links and arms of a rear suspension are attached to a rear sub frame and then this rear sub frame is attached to a kick-up portion and rear frames of a vehicle body, is known.
Herein, the rear sub frame which comprises a pair of side members extending in a vehicle longitudinal direction at both sides, in a vehicle width direction, of the vehicle body and cross members extending in the vehicle width direction and interconnecting the pair of side members is known, for example. The rear sub frame of the automotive vehicle having rear wheels as driving wheels, in which a front cross member of the cross members is configured in substantially a V shape in a front view and a bottom portion of the front cross member which corresponds to an apex portion of the V shape is located below a rear differential of the vehicle, is also known (see US Patent Application Publication No. 2009/0212548 A1, for example).
The rear sub frame has been required to have a high rigidity for improving the responsiveness of the suspension and the like during the vehicle traveling and also to provide an appropriate NVH (noise-vibration-harshness) performance. It is preferable that the side members and the cross members of the rear sub frame be configured in as a more straight shape as possible in order to improve the NVH performance properly. Further, it is necessary that the side members and the cross members do not interfere with an exhaust pipe or the like arranged below a rear portion of the vehicle body. However, the cross member of the conventional rear sub frame disclosed in the above-described patent document includes a bending portion for avoiding any interference with the exhaust pipe or the like. In this case, since complicated vibration modes are caused by the shape of the bending portion of the cross member, it may be difficult to improve the NVH performance properly. Further, it is necessary to reinforce the cross members and the side members in order to suppress such vibration modes which has a bad influence on the NVH performance, so that the weight of the rear sub frame may become heavier improperly.